Infusion pumps and other devices are used regularly for subcutaneous injections of therapeutic fluids, drugs, proteins, and other compounds for humans or animals. Such delivery systems and methods are used also for insulin delivery. A conventional infusion pump is an infusion device specifically adapted for infusing a drug to the subcutaneous tissue using an infusion set connecting the drug reservoir within the pump to a catheter adhered to the skin. The pump and infusion set can be disconnected and reconnected to the catheter leaving only the catheter on the skin when the user desires, for example, before swimming or taking a shower or other activities that might harm the pump or when the pump might disturb the activity. Typically, the infusion set including the catheter is replaced regularly, usually every three days.
Infusion pumps may deliver medicament around the clock. For example, an infusion pump may provide a slow drip of medicament that may be increased by the user or by other input before an event that requires a large amount of medicament. For diabetics, insulin infusion pumps deliver basal insulin around the clock, in addition to a bolus dose of insulin, which may be adjusted by the user, to be delivered by the infusion pump before, during, or immediately after a meal. It is desired that the bolus dose of drug or insulin reaches the circulatory system quickly, and provides an amount of insulin that matches the amount of carbohydrates consumed by the patient. This fast acting delivery to the circulatory system is not required for the basal drip.
It is estimated that a large number of infusion pumps are being used today by hundreds of thousands of diabetics worldwide. Introducing a new pump to the market is a process that may take a few years, and it could take many years to phase out existing pumps. Additionally, diabetic patients who are required to receive several procedures per day to control their blood glucose level will be reluctant to adopt new treatments that will require them to perform additional procedures on top of the procedures they already receive.
When a diabetic patient consumes food, his or her level of glucose rises. Unfortunately, existing subcutaneous injection devices, including infusion pumps, are incapable of quickly matching or preventing the rise of blood glucose. The delay in such matching is also true in case of “rapid-acting” insulins. Some of the reasons for this delay include a lag in the absorption of insulin from the time insulin is injected at the injection site to the time it takes for complex insulin molecules to break down into monomers.
Additionally, since blood glucose levels rise shortly following the meal, the delay in matching insulin to the rising glucose level may cause a post prandial hyperglycemic event (i.e., when the blood glucose level is above normal) to occur. Furthermore, after a certain period of time passes after a meal (e.g., 2-3 hours), the blood glucose level could drop while the insulin concentration in the blood rises followed by the peak of the systemic insulin effect. This may cause a hypoglycemic event (i.e., when the blood glucose level is below normal) to occur. Both hyperglycemic and hypoglycemic events are highly undesirable. Additionally, since local blood perfusion at the insulin injection region, including that of insulin infusion set connected to insulin infusion pump, has large variability, depending on the ambient temperature and other parameters, it induces large variations to the delay of the peak of time profile of the insulin action. Those variations in the insulin peak action period further increase the variability in the blood glucose level.
Additionally, it is known that certain drugs, including insulin, are growth hormones. These drugs, when injected several times at the same location, can cause local cell growth, causing Lipohypertrophy. Using regular infusion sets and infusion pumps, the drug may be infused several times per day, and possibly for several days, at the same location, which could result in Lipohypertrophy. Increasing local blood perfusion at the injection site to promote drug uptake to the circulatory system may reduce the unwanted Lipohypertrophy phenomenon.
Therefore, it is desirable to provide a system and method that provide efficient and rapid uptake of infused drug to the circulatory system when the drug is infused by an infusion pump, that are compatible with existing infusion pumps. In particular, it is desirable to provide a system and method for injection of insulin to the user through an unmodified infusion pump without requiring additional (extra) efforts from the user while using the pump and infusion set. Additionally, it is desirable to provide a system and method that provide treatment only in instances where the pump delivers bolus insulin doses to maintain a normal blood glucose level and prevent or reduce hyperglycemic and hypoglycemic events, and reduce Lipohypertrophy.